*{
  margin: 0;
  padding: 0;
}
html,body,#root,.box{
  width: 100%;
  height: 100%;

}
.box{
  display: flex;
  flex-direction: column;

}
.box header,.box footer{
  width: 100%;
  height: 50px;
  background-color: skyblue;
}
.box main{
  flex: 1;
}
.box a{
  color: black;
  text-decoration: none;
}
.box .active{
  color: red;
}
